====== CORS - cross-origin resource sharing ======
  * [[https://developer.mozilla.org/en-US/docs/HTTP/Access_control_CORS|HTTP access control (CORS) - HTTP]]
  * [[http://enable-cors.org/|enable cross-origin resource sharing]]
  * [[https://homoefficio.github.io/2015/07/21/Cross-Origin-Resource-Sharing/|Cross Origin Resource Sharing - CORS]]
  * [[https://developer.mozilla.org/ko/docs/Web/HTTP/Access_control_CORS|HTTP 접근 제어 (CORS) - HTTP | MDN]]
  * [[https://www.javacodegeeks.com/2018/09/really-know-cors.html|Do You Really Know CORS? | Java Code Geeks - 2018]]